1. Field
Aspects of the present invention relate to a light-emitting device, and more particularly, to a blue light-emitting device having high color characteristics, and an organic light-emitting display including the blue light-emitting device.
2. Description of the Related Art
Generally, an organic light-emitting device (OLED) includes an anode, a cathode, and an organic light-emitting layer. The organic light-emitting layer has a functional thin film form and is disposed between the anode and the cathode. In the OLED, a hole and an electron are injected into the organic light-emitting layer respectively from the anode and the cathode where they combine to form an exciton, which emits light.
The OLED is classified into a passive matrix (PM) type using a passive driving method, and an active matrix (AM) type using an active driving method, according to a method of driving the OLED. In a PM type OLED (PM-OLED), anodes and cathodes are respectively arranged in columns and rows, and a scanning signal is supplied to the cathodes from a row driving circuit to select one of the rows. Also, a column driving circuit inputs a data signal to each pixel. In an AM type OLED (AM-OLED), a signal input to each pixel is controlled by using a thin-film transistor (TFT). The AM-OLED is suitable for processing a large number of signals, and thus is mostly used as a display for realizing a moving image.
A red, green, and blue (RGB) independent deposition method using a fine metal mask (FMM) is mostly used to obtain a full color OLED that is practical and mass-producible. The RGB independent deposition method forms patterns according to each color by using the FMM. Also, the RGB independent deposition method uses micro-cavity technology for forming a semi-transmission mirror and a total reflective mirror so as to increase color characteristics. The micro-cavity technology, which is mostly used in a mobile AM-OLED, is a top-emission (TE)-OLED micro-cavity technology involving a high aperture ratio.
FIG. 1 is a diagram schematically illustrating a conventional TE-OLED having a resonance structure. Referring to FIG. 1, R. G, and B light-emitting devices respectively resonate light generated in light-emitting layers. The light-emitting layers are disposed between anodes 102r, 102g, and 102b and cathodes 105r, 105g, and 105b, on a substrate 101. The anodes 102r, 102g, and 102b and the cathodes 105r, 105g, and 105b each include a reflective layer. The resonated light passes through the cathodes 105r, 105g, and 105b. 
Optical distances Lr, Lg, and Lb are respectively between the anodes 102r, 102g, and 102b, and the cathodes 105r, 105g, and 105b in each R. G, and B pixel. The optical distances Lr, Lg, and Lb are adjusted according to a thickness of the cathodes 105r, 105g, and 105b or a thickness of an organic layer. Light emitted outside the conventional TE-OLED according to resonance has a smaller full width at half maximum (FWHM), has an increased intensity at a peak wavelength, and a higher color gamut than before it is resonated. However, in order for the resonance structure to maintain color characteristics, a thickness of a resonator must be maintained within a process margin of 1%. Accordingly, an OLED needs to be developed which has excellent color characteristics and an excellent process margin.